1. Field of the Invention
The present invention relates to a compact self-propelled stress test exercise device which simulates the mechanical action, and work expenditure a subject would experience while climbing stairs. The invention permits the subject to exercise against graded levels of resistance scaled to the subject's own weight, and applied to a friction belt which rides in contact with a flywheel. Output energy is proportional to the rate at which the subject climbs within the device as well as the weight of the subject.
2. Description of the Prior Art
Numerous devices have been marketed for the purpose of providing graded levels of exercise as a means toward evaluating the physiological condition of a patient, in particular the cardiovascular performance of a patient, during application, and immediately following application of the exercise. One commonly used exercise apparatus for such stress testing is the electric treadmill which consists of an elongated platform of rollers over which an endless belt is driven by an electric motor. Such a device is described in U.S. Pat. No. 3,703,284 entitled "Diagnostic and Therapeutic Exercise Treadmill". In using such apparatus, the patient must continue to pace himself so as to "keep-up" with the speed of the endless belt. The starting and stopping of such devices can be dangerous, and the clinical operator must constantly and alertly monitor the patient to prevent accidents. Although several protective arrangements have been utilized, as for example those described in U.S. Pat. No. 3,711,812 entitled, "Drive and Control Systems for Diagnostic and Therapeutic Exercise Treadmill", treadmills nevertheless remain potentially dangerous even though adequate precautions are taken. What is actually desired is a compact, simple, safe exercising device which will provide the work loading necessary for a submaximal stress test of a person's cardiovascular system comparable between persons of various weights with all the energy generated by the patient functioning as the sole prime mover.
Accordingly, a primary object of the present invention is to provide a safe self-propelled stress test exercise device which is simple to build and operate, and which gives comparable test results between patients of varying body weight.
A further object of the invention is to provide a stress test exercise device which will simulate a common activity so as to provide exercise to achieve high heart rates together with an accurate indication of both the instantaneous and cummulative energy delivered by the patient while engaging in the activity.
Although some attempts have been made to ameliorate the problems associated with traditional treadmills, these devices have in turn created other problems. In U.S. Pat. No. 3,826,491 entitled "Exercise Treadmill" the treadmill is elevated at one end to simulate an inclined walking surface. Such devices however can create problems at high inclination angles - and sufficient friction must be maintained with respect to the drive system to preclude the possibility of undesirable belt movement under such conditions.
Another shortcoming of traditional externally powered stress test exercise devices lies in the fact that the forces over which body energy is measured are not well defined for purposes of determining power output. It is well known for example that the efficiency of a muscle is dependent upon the nature of the imposed load. Thus, a pure resistive force theoretically produces no energy output until there is movement--yet such forces rapidly tire the muscle as a result of the body energy expended in maintaining a counter force. It is therefore desirable that the human output from any self-powered exercise device be related to measurable energy units, and that the measurable quantities be indicative of the physiological output. Moreover, the physiological effort should not rapidly deplete the muscles used to maintain the output--i.e., the effort should involve a large muscle mass in such a way that the muscles function in their usual manner to carry out a common or representative activity over an extended period of time.
Accordingly, a further object of the invention is to provide a stress test exercise device for measuring sustained physiological energy output.
Another object of the invention is to provide a stress test exercise device which functions to provide relatively consistent correlations between the physiological energy dissipated and the measurable mechanical energy outputted.
Although traditional self-powered stress test exercise devices such as stationary bicycles and rowing machines are partially effective for accomplishing the above objectives, they have some complications in terms of their capability of establishing comparable stress loadings between patients of various limb lengths and body weights. Self propelled and motor actuated bicycle ergometers have been used to apply various stages of work loading for physiological stress testing but they have the disadvantage of using muscle motion few people are prepared to carry to the required energy levels and they do not provide a simple correlation of results by loadings calibrated to body weight. What is actually desired is a device which will accurately and consistently provide useful, comparable stress test exercise for patients of various body weights, independent of varient styles of use and immune to variations for all users, accordingly:
A further object of the invention is to provide a self-powered stress testing device wherein the stress test loading is at graded levels proportional to the weight of the patient and substantially independent of the method or style of use.
Another object of the invention is to provide a safe self-powered stress test exercise loading apparatus which will facilitate the measurement of energy output while the patient performs a simulated common activity such as climbing stairs without gaining sufficient height to be injured by a fall.
Another object of the invention is to provide a self-powered stress test exercise device which can be easily switched from one level of load to another.
Another object of the invention is to provide a stress test exercise device which may be operated at comparable effective stress rates for all users.
Another object of the invention is to provide a variable resistance load which can be applied by either weights or springs or both in earth's gravity or outside of it.
A further object of the invention is to provide a stress test exercise device which can be utilized in a weightless space environment.
Another object of the invention is to provide an elastic suspension arrangement for a self-powered pedal platform exercising device.
Another object of the invention is to provide a visual readout of the cumulative energy expended during a particular time interval.
Another object of the invention is to provide a visual readout of the instantaneous rate at which energy is expended by the operator.
Other objects and advantages of the present invention will be obvious from the detailed description of a preferred embodiment given herein below: